Best Peptides for Weight Loss

1. Tirzepatide

Tirzepatide is a dual agonist that activates both GIP (glucose-dependent insulinotropic polypeptide) and GLP-1 receptors, combining two incretin pathways for appetite suppression, improved insulin sensitivity, and weight loss. Trials show it produces greater average weight loss than semaglutide. Like other incretin mimetics it is titrated slowly to manage GI side effects. It strongly moves metabolic markers and is used as a standalone metabolic intervention. Monitor blood glucose, especially if combined with other glucose-lowering agents.

• Weight Loss (grade S) — 2 cited studies through 2023
• Immune Function (grade B) — post-hoc SURMOUNT hsCRP/IL-6 analyses, not a primary-endpoint RCT
• Body Composition (grade B) — DEXA sub-analyses of Phase 3 trials show fat-mass-dominant loss
• Muscle Growth (grade D) — no muscle-growth benefit; DEXA sub-analyses show lean mass falls with total weight
• Sleep Quality (grade D) — 1 cited study through 2024

Strongest study: SURMOUNT-OSA, NEJM (2024) — AHI -27 vs -5 placebo · OSA-with-obesity only · downstream effect of weight loss, not direct sleep mechanism · N=469

Full Tirzepatide reference

2. Semaglutide

Semaglutide is a long-acting GLP-1 (glucagon-like peptide-1) receptor agonist that slows gastric emptying, increases satiety, and improves insulin sensitivity and glucose control. Originally developed for type 2 diabetes, it has become a leading weight-loss therapy. Dosing is titrated up slowly over weeks to minimize gastrointestinal side effects like nausea. It directly affects metabolic markers — expect improvements in HbA1c, fasting glucose, and body composition. Not typically stacked with growth or healing peptides; used as a standalone metabolic tool.

• Weight Loss (grade S) — 3 cited studies through 2023
• Immune Function (grade B) — post-hoc STEP proteomic and inflammation sub-analyses, not a primary-endpoint RCT
• Body Composition (grade B) — DEXA sub-analyses of Phase 3 trials show fat-mass-dominant loss
• Muscle Growth (grade D) — no muscle-growth benefit; DEXA sub-analyses show lean mass falls with total weight
• Cognitive Function (grade D) — 1 cited study through 2024

Strongest study: EVOKE / EVOKE+, Alzheimers Dement (2026) — missed primary endpoint in early Alzheimer's · readout Mar 2026 · N=1840

Full Semaglutide reference

3. Retatrutide

Retatrutide (LY3437943) is an investigational triple receptor agonist that activates the GIP, GLP-1, and glucagon receptors — informally a ‘GLP-3’ for adding glucagon agonism on top of the dual mechanism of tirzepatide. The added glucagon activity raises energy expenditure alongside the appetite suppression and improved glucose control of the incretin pathways, and phase 2 trials reported some of the largest average weight reductions seen for any single agent to date. It is dosed once weekly subcutaneously and titrated slowly to manage gastrointestinal side effects. As an investigational compound it is not FDA-approved; monitor metabolic markers and titrate per protocol.

• Weight Loss (grade A) — 3 cited Phase 3 trials through 2025, investigational, not yet approved
• Immune Function (grade D) — no human immune-outcome trial exists, preclinical rationale only
• Body Composition (grade B) — TRIUMPH DEXA sub-analyses; ~25% of total loss is lean tissue
• Muscle Growth (grade D) — 1 cited study through 2025

Strongest study: TRIUMPH-1, NEJM (2025) — -28.3% body weight @ 80wk · N=2339

Full Retatrutide reference

4. Liraglutide

Liraglutide is a GLP-1 receptor agonist with 97% sequence homology to human GLP-1, modified with a fatty-acid side chain for albumin binding and extended action. Unlike the once-weekly semaglutide and tirzepatide, liraglutide requires once-daily subcutaneous dosing, titrated slowly upward to limit gastrointestinal side effects. It's FDA-approved under two brand names: Victoza for type 2 diabetes and Saxenda for chronic weight management, each with its own titration schedule and maximum dose. As an older, well-characterized GLP-1, it has the longest real-world safety record of any compound in this class.

Full Liraglutide reference

5. Orforglipron

Orforglipron is a fundamentally different kind of GLP-1 medicine: a small-molecule, non-peptide oral GLP-1 receptor agonist, taken as a once-daily tablet at any time of day, with or without food — unlike semaglutide's oral form (Rybelsus), which must be taken fasted with a small sip of water and a 30-minute food/drink delay. Developed by Eli Lilly under the development code LY3502970, orforglipron received FDA approval on April 1, 2026 under the brand name Foundayo, for adults with obesity or overweight with a weight-related medical problem. Its inclusion here alongside injectable peptides mirrors how MK-677 — also a non-peptide, orally active compound — sits in REGEN's catalog as a notable exception to the peptide-only norm.

Full Orforglipron reference

6. 5-Amino-1MQ

5-Amino-1MQ is a small-molecule inhibitor of NNMT (nicotinamide N-methyltransferase), an enzyme that helps fat cells store energy and that's been linked to obesity and metabolic dysfunction. In diet-induced-obese mice, blocking NNMT with 5-Amino-1MQ cut body weight by roughly 7%. It is not a peptide — it's a small molecule, popular in the same longevity/fat-loss research circles as NAD+ and MOTS-c. As of 2026, all efficacy evidence is animal-only; no human trial has been published.

• Weight Loss (grade C) — Neelakantan 2018 (Biochem Pharmacol): -7% body weight in a diet-induced-obesity mouse model. No human trials published.

Strongest study: Neelakantan diet-induced obesity, Bioorg Med Chem Lett (2018) — -7% body weight in obese mice; zero published human trials

Full 5-Amino-1MQ reference